AB0056 COMPARATIVE ANALYSIS OF THE DISTRIBUTION OF LYMPHOCYTES, MACROPHAGES AND MAST CELLS IN THE MARGINAL SYNOVIUM AND JOINT CAPSULE IN GENERAL AFTER ANTENATAL ANTIGENIC STIMULATION
Authors: A. Fedotchenko
Journal: Annals of the Rheumatic Diseases (2022)

Background The joint capsule is one of the main pathogenetic points of arthritis development [1]. In addition, the initial signs of the inflammatory joint diseases are identified primarily in the marginal transitional zone [2]. The joint capsule morphology was studied using hip joints of Wistar rats during the postnatal period in norm and after antigenic stimulation. The last one was modeled through the transuterine intrafetal interscapular subcutaneous injection of antigen (0.05 ml of human normal immunoglobulin) for the rat foetus on the 18th day of its antenatal life under general anesthesia and sterile conditions via laparotomy for the pregnant female (Voloshynʼs method (1981). The control group of rats was injected with 0.05 ml of physiological saline in the same manner. The earlier recovery of certain parameters (total cells quantity, vessels, collagen fibers and ground substance) to normality in the marginal synovium compared to the rest (larger) part of the joint capsule in antigen-suppressed rats was previously revealed. Objectives A comparative analysis of the distribution of lymphocytes, macrophages and mast cells in the marginal synovium in relation to the rest (larger) part of the joint capsule after antenatal antigenic stimulation was conducted. Methods Collection of the biomaterial was carried out on the first, seventh, 14th, 30th, 45th, 60th and 90th day of postnatal life under general anesthesia (intact, antigen-suppressed and control rats; six rats in each group, 126 rats in total). The joints were fixed, decalcified and dehydrated. Paraffin-embedded tissue sections were stained with hematoxylin and eosin. Cells of the synovial subintima of the marginal synovium and rest (larger) part of the joint capsule were counted using the light microscopy (x100) and morphometric lattice. The obtained data were processed using the statistical methods. The parameters of intact and control rats did not differ significantly from each other. Results In the joint capsule of antigen-suppressed rats compared to intact and control rats, an increased number of lymphocytes till the 90th day (in the marginal synovium – till the 45th day), macrophages till the seventh day (in the marginal synovium – also till the seventh day) and mast cells till the 90th day (in the marginal synovium – till the 14th day) was found. The integrity of the synovium-cartilage barrier is of fundamental importance, failing which it would lead to excessive synovial tissue penetration into the articular cartilage, recognition of it by immunocompetent cells and initiation of immune-mediated cartilage destruction. The previously premature appearance (on the seventh day) of strong expression of receptors for peanut agglutinin (PNA) in the marginal cartilage of antigen-suppressed rats I detected could lead to the assumption about the premature appearance of “chondroprotective substances” such as fibronectin, laminin etc. and their intensive glycosylation. This fact might be considered a compensatory mechanism to create the „defensive wall” for adhesion and deactivation of the immunocompetent cells, therefore reducing their influence on cells and contributing to accelerated return the parameters to normality. Conclusion The compensatory defenсe mechanisms, occurring in the marginal cartilage after the antigenic stimulation, contribute to earlier recovery of parameters in the marginal synovium compared to the joint capsule in general. In so doing, the marginal transitional zone forms the important innate, nonspecific, immunobiological, anatomical and physiological barrier between the joint capsule and articular cartilage. References [1]Mathiessen A, Conaghan PG: Synovitis in osteoarthritis: current understanding with therapeutic implications. Arthritis Res Ther. 19. 18 (2017). [2]Allard SA, Bayliss MT, Maini RN: The synovium-cartilage junction of the normal human knee. Implications for joint destruction and repair. Arthritis Rheum. 33(8). 1170–9 (1990). Disclosure of Interests None declared